Driving assistance device and driving assistance method

Abstract

An ECU as a driving assistance device has a traffic sign detection section, a lane entry detection section and a judgment section. The traffic sign detection section detects traffic signs including a speed limit symbol based on front-image data captured by an in-vehicle camera. The lane entry detection section detects that the own vehicle has entered a ramp lane to leave a highway. The judgment section detects an extent of a current driving lane as the ramp lane when following conditions (c1) and (c2) are satisfied after the lane entry detection section detects the entry of the own vehicle into the ramp lane: (c1) not less than two traffic signs are arranged along the current driving lane in forward direction of the vehicle; and (c2) an arrangement of speed limit symbols included in the detected traffic signs satisfy a predetermined speed reduction pattern.

What is claimed is: 
     
       1. A driving assistance device including a central processing unit (CPU), comprising:
 a traffic sign detection section capable of detecting, using the CPU, traffic signs including at least a speed limit symbol on a basis of front image data captured by an in-vehicle camera mounted on an own vehicle; 
 a lane entry detection section capable of detecting, using the CPU, that the own vehicle is entering a connection lane through which the own vehicle leaves a highway; and 
 a judgment section capable of determining, using the CPU, that a current driving lane, on which the own vehicle travels, is the connection lane when a first condition, a second condition and a third condition are satisfied after the lane entry detection section has detected entry of the own vehicle into the connection lane, 
 wherein 
 the first condition indicates that the traffic sign detection section detects not less than two traffic signs arranged along the current driving lane in a forward direction of the own vehicle, and 
 the second condition indicates that a speed reduction pattern indicated by speed limit symbols included in the traffic signs detected by the traffic sign detection section in the forward direction of the own vehicle satisfies a predetermined speed reduction pattern, and 
 the third condition indicates that a distance between the traffic signs detected by the traffic sign detection section in the forward direction of the own vehicle is narrower than a predetermined distance. 
 
     
     
       2. The driving assistance device according to  claim 1 , wherein
 the judgment section detects an end place of the connection lane, when the speed reduction pattern indicated by the speed limit symbols included in the traffic signs detected by the traffic sign detection section in the forward direction of the own vehicle is different from the predetermined speed reduction pattern, or when a distance between the detected traffic signs adjacent to each other is wider than a predetermined distance, and 
 the judgment section detects an extent of the connection lane as being from a place of entrance of the connection lane detected by the lane entry detection section to the end place of the connection lane. 
 
     
     
       3. The driving assistance device according to  claim 1 , further comprising:
 a notification control section capable of notifying, using the CPU, to a driver of the own vehicle through a notification unit, information regarding that the own vehicle now travels on the connection lane and a speed limit value corresponding to the speed limit symbol included in a detected traffic sign at a current location of the own vehicle when the own vehicle travels on the connection lane detected by the judgment section. 
 
     
     
       4. The driving assistance device according to  claim 1 , wherein
 the judgment section uses the predetermined speed reduction pattern which indicates that the speed limit symbols included in the detected traffic signs have different speed limit values to each other, and being reduced in the forward direction of the own vehicle. 
 
     
     
       5. The driving assistance device according to  claim 1 , further comprising:
 a distance detection section capable of detecting, using the CPU, a distance in a width direction of the own vehicle between the own vehicle and a detected traffic sign, which includes an exit symbol and the speed limit symbol, the exit symbol providing for the own vehicle to leave the highway and enter the connection lane; and 
 a driver's intention detection section capable of detecting, using the CPU, a driver's intention for the own vehicle to change the current driving lane, 
 wherein the lane entry detection section detects that the own vehicle has entered the connection lane when: 
 the traffic sign detection section has detected the traffic signs including the exit symbol and the speed limit symbol; 
 the distance detected by the distance detection section is narrower than a predetermined distance; and 
 a direction of the own vehicle when changing the current driving lane detected by the driver's intention detection section is equal to a direction of the traffic signs including the exit symbol and the speed limit symbol. 
 
     
     
       6. A driving assistance device including a central processing unit (CPU), comprising:
 a traffic sign detection section capable of detecting, using the CPU, traffic signs including at least a speed limit symbol on a basis of front image data captured by an in-vehicle camera mounted on an own vehicle; 
 a lane entry detection section capable of detecting, using the CPU, that the own vehicle is entering a connection lane through which the own vehicle leaves a highway; 
 an end place detection section capable of detecting, using the CPU, an end place of the connection lane based on a distance from an entrance of the connection lane; and 
 a judgment section capable of determining, using the CPU, that a current driving lane, on which the own vehicle travels, is the connection lane when a condition is satisfied after the lane entry detection section has detected the entry of the own vehicle into the connection lane, 
 wherein the condition indicates that the end place of the connection lane has being detected. 
 
     
     
       7. The driving assistance device according to  claim 6 , wherein
 the end place detection section detects an end place of the connection lane, when a speed reduction pattern indicated by speed limit symbols included in the traffic signs detected by the traffic sign detection section in a forward direction of the own vehicle is different from a predetermined speed reduction pattern, or when a distance between the detected traffic signs adjacent to each other is wider than a predetermined distance, and 
 the judgment section detects an extent of the connection lane as being from a place of entrance of the connection lane detected by the lane entry detection section to the end place of the connection lane. 
 
     
     
       8. The driving assistance device according to  claim 6 , further comprising:
 a notification control section capable of notifying, using the CPU, to a driver of the own vehicle through a notification unit, information regarding that the own vehicle now travels on the connection lane and a speed limit value corresponding to the speed limit symbol included in a detected traffic sign at a current location of the own vehicle when the own vehicle travels on the connection lane detected by the judgment section. 
 
     
     
       9. The driving assistance device according to  claim 6 , wherein
 the judgment section uses a predetermined speed reduction pattern which indicates that the speed limit symbols included in the detected traffic signs have different speed limit values to each other, and being reduced in a forward direction of the own vehicle. 
 
     
     
       10. The driving assistance device according to  claim 6 , further comprising:
 a distance detection section capable of detecting, using the CPU, a distance in a width direction of the own vehicle between the own vehicle and a detected traffic sign, which includes an exit symbol and the speed limit symbol, the exit symbol providing for the own vehicle to leave the highway and enter the connection lane; and 
 a driver's intention detection section capable of detecting, using the CPU, a driver's intention for the own vehicle to change the current driving lane, 
 wherein the lane entry detection section detects that the own vehicle has entered the connection lane when: 
 the traffic sign detection section has detected a traffic sign including the exit symbol and the speed limit symbol; 
 the distance detected by the distance detection section is narrower than a predetermined distance; and 
 a direction of the own vehicle when changing the current driving lane detected by the driver's intention detection section is equal to a direction of the traffic sign including the exit symbol and the speed limit symbol. 
 
     
     
       11. A driving assistance device including a central processing unit (CPU), comprising:
 a traffic sign detection section capable of detecting, using the CPU, traffic signs including at least a speed limit symbol on a basis of front image data captured by an in-vehicle camera mounted on an own vehicle; 
 a lane entry detection section capable of detecting, using the CPU, that the own vehicle is entering a connection lane through which the own vehicle leaves a highway; and 
 a notification control section capable of performing (a) and (b), using the CPU, when the traffic sign detection section detects that speed limit symbols included in the traffic signs detected by the traffic sign detection section indicate a speed reduction pattern, 
 (a) the notification control section sequentially notifies, to a driver of the own vehicle, speed limit values based on the detected speed limit symbols as the speed reduction pattern when the lane entry detection section detects that the own vehicle has entered the connection lane, and 
 (b) the notification control section does not notify, to the driver of the own vehicle, the speed limit values when the lane entry detection section does not detect that the own vehicle has entered the connection lane. 
 
     
     
       12. The driving assistance device according to  claim 11 , further comprising:
 an end place detection section that detects, using the CPU, an end place of the connection lane, when a speed reduction pattern indicated by the speed limit symbols included in the traffic signs detected by the traffic sign detection section in a forward direction of the own vehicle is different from a predetermined speed reduction pattern, or when a distance between the detected traffic signs adjacent to each other is wider than a predetermined distance; and 
 a judgment section that detects, using the CPU, an extent of the connection lane as being from a place of entrance of the connection lane detected by the lane entry detection section to the end place of the connection lane. 
 
     
     
       13. The driving assistance device according to  claim 11 , wherein
 the notification control section capable of notifying, to the driver of the own vehicle through a notification unit, information regarding that the own vehicle now travels on the connection lane and the speed limit values corresponding to the speed limit symbols included in the detected traffic signs at a current location of the own vehicle when the own vehicle travels on the connection lane. 
 
     
     
       14. The driving assistance device according to  claim 11 , wherein the notification control section uses a predetermined speed reduction pattern which indicates that the speed limit symbols included in the detected traffic signs have different speed limit values to each other, and being reduced in the forward direction of the own vehicle. 
     
     
       15. The driving assistance device according to  claim 11 , further comprising:
 a distance detection section capable of detecting, using the CPU, a distance in a width direction of the own vehicle between the own vehicle and a detected traffic sign, which includes an exit symbol and the speed limit symbol, the exit symbol providing for the own vehicle to leave the highway and enter the connection lane; and 
 a driver's intention detection section capable of detecting, using the CPU, a driver's intention for the own vehicle to change a current driving lane, 
 wherein the lane entry detection section detects that the own vehicle has entered the connection lane when: 
 the traffic sign detection section has detected the traffic signs including the exit symbol and the speed limit symbol; 
 the distance detected by the distance detection section is narrower than a predetermined distance; and 
 a direction of the own vehicle when changing the current driving lane detected by the driver's intention detection section is equal to a direction of the traffic signs including the exit symbol and the speed limit symbol.